This invention relates to a flat plate dialyzer and method of making same and more particularly to a compact unit readily adaptable to mass production which has improved distribution of fluids therein.
Most prior art flat plate dialyzers are constructed of rigid support material interleaved with permeable membrane which are stacked and clamped together. Typical of this type of dialyzer are the devices illustrated in Esmond U.S. Pat. Nos. 3,585,131 and 3,738,495. These devices are bulky, difficult to assemble and because of the amount of plastic material used in them are not practical for disposal after use.
Attempts have been made to substitute the rigid support material of the Esmond U.S. Pat. Nos. 3,585,131 and 3,738,495 devices with flexible open weave support material such as illustrated in Leonard U.S. Pat. No. 3,757,955, Esmond U.S. Pat. No. 3,780,870 and Markley U.S. Pat. No. 3,788,482. A problem common to all of these devices, however, is inadequate distribution of fluids within the dialyzer, more particularly, distribution of fluid to the full depth of the device so the fluids will not shunt or shortcircuit the mass transfer area and go directly from the fluid inlet to the outlet. The Esmond U.S. Pat. No. 3,780,870 device discloses one approach to solving this problem, i.e., a complicated assemblage of support material having varying widths (reference numerals 14, 15 and 16 in FIG. 2 of Esmond). Another approach is disclosed in Leonard U.S. Pat. No. 3,757,955 which uses a stiff backing with stragetically located slots in it to promote distribution of fluids (FIG. 22; col. 9). All of these approaches, however, have the distinct disadvantage that they materially increase the cost of manufacture and do not lend themselves to automated assembly.
Other problems associated with use of flexible support material are the difficulty in sealing the permeable membrane within a housing so that there will be no leakage between the fluids (such as blood and dialysate) on opposite sides of the membrane and excessive bulk created when the support material is folded. Markley U.S. Pat. No. 3,788,482 attacks the first problem by embedding the leading and trailing edge of the membrane in an inner housing of epoxy (reference numeral 14 in FIG. 2), but this also has the disadvantage of being impractical from a manufacturing standpoint. None of the prior art treats the problem of excessive bulk and in fact compounds the problem by using multiple layers of support material in each pleat (Esmond U.S. Pat. No. 3,780,870) and extra layers of backing material with the support material (Leonard U.S. Pat. No. 3,757,955).